Electric circuit



A. VAN DE WlEL ELECTRIC CIRCUIT Nov. 4, 1952 4 sheets-S1196: 1

Filed NOV. 25, 1949 VOLTAGE CONTROL DEVICE mm! In 03%??? Nov. 4, 1952 A. VAN DE WIEL 7,

ELECTRIC CIRCUIT Filed Nov. 25, 1949 4 Sheets-Sheet 2 SECOND VOLTAGE LOAD CONTROL DEVICE FIRST LOAD VOLTAGE CONTROL DEVICE SECOND LOAD VOLTAGE CONTROL DEVICE INVENTOR. NF'l-d Van De wie\ AGENT A. VAN DE w||-:| 2,617,085

ELECTRIC CIRCUIT Nov. 4, 1952 SECOND LOAD 22 VOLTAGE FIRST LOAD CONTROL DEVICE v E VOLTAGE CONTROL 9 34 -30 DEVICE c A A 33 32 33 2s 30 3| 32 35 29 I INVENTOR.

. AFred Van De wiel Nov. 4, 1952 A. VAN DE WlEL ,617,0

ELECTRIC CIRCUIT Filed Nov. 25, 1949 4- Sheets-Shut 4 l TAGE CONTROL DEVICE VOLTAGE CONTROL FIRST LOAD DEVICE IN V EN TOR.

Al ved Van De Niel AGENT Patented Nov. 4, 1952 ELECTRIC CIRCUIT Alfred van de Wiel, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application November 25, 1949, Serial No. 129,203 In the Netherlands December 23, 1948 9 Claims.

This invention relates to a rectifying circuitarrangement comprising at least two multi-phase rectifying circuits comprising controllable, gasor vapour-filled rectifiers. The invention is characterized in that the rectifying circuit-arrangements are connected to the same supply transformer winding and in that at least one of multiphase rectifiers are connected with their cathodes to the said transformer windings, so that these cathodes, relative to the neutral point of the transformer, have an alternating cathode voltage. The invention is further characterized in that each of the control-electrodes of the lastmentioned rectifiers is connected to the neutral point of the supply transformer by way of a combination of a common direct control-voltage, an alternating voltage superposed thereon and an alternating compensation voltage, with the use of which the voltage between the cathodes and the said neutral point, which voltage is liable to produce and undue alternating voltage between the control-electrodes and the cathodes, is compensated.

In the present case, the aforesaid superposed alternating voltage is a sine voltage of a frequency equal to that of the alternating supply voltage.

This rectifying circuit-arrangement has the advantage that atleast two of the niulti-pha'se rectifying circuits may each be connected to a separate load to be differently controlled. If, in

former, only one pair of cathodes could be earthed. Since the neutral point of the transformer can then no longer be earthed, the' neutral point is connected to the variable direct voltage of the load to be controlled, which voltage is connected to the earthed cathodes. second pair of cathodes is connected through the second load to the said neutral point of which the voltage varies so that accurate control of the second load is no longer possible. I In this event, in efiect, the current flowing through the second load likewise depends upon the voltage at the neutral point which constitutes one terminal of the load. The disadvantage that at least one pair of cathodes has analternating voltage applied to it, is obviated by the compensating alternating voltage across the controlcircuit. Instead of using a double-wound transformer, use may be made of an auto-transformer.

The direct control-voltage may, .for example,

The

be taken from the load for constant voltage control with a varying load,- more particularly for controlling D. C. motors.

In order that the invention may be readily carried into efiect; anumber of examples will now be described in detail with reference to the accompanying drawings.

In the drawing:

Fig. 1 is aschematic diagram of a preferred embodiment of a two-phase rectifying circuit in accordance with the invention; M

Fig. 2 are curves illustrative of voltage relationships existing in the circuit of Fig. 1; 4

Fig. 3 is a vector diagram of voltage relationships existing in the circuit of Fig. 1;

Fig. 4 is acircuit diagram of another preferred embodiment of the invention; H I H Fig. 5 is a circuit diagram of still another preferred embodiment of the invention; v v

Fig. ,6 is a vector diagram illustrative of voltage relationships existing in the circuit of Fig. 5;

Fig. 7 is a vector diagram illustrative of the relationships existing in the circuit of Fig. 5;

Fig. 8 is a circuit diagram of a still further embodiment of the invention; 7 i

Fig. 9 is a circuit diagram of a prefer red embodiment of a three-phase rectifier system in accordance with the invention; p 7 i Fig. 10 is a vector diagram illustrative of the voltage relationships existing in the circuit of Fig. 11 is a circuit arrangement of a control apparatus for use in conjunction with the preferred embodiments of the invention and Fig. 12 is a schematic diagram of a preferred;

embodiment" of yet another two-phase rectifier system in accordance with the invention. i

In Fig. 1 the power line voltage terminals I and 2 are connected to atransformer 3; the secondary winding of which is connected in twophase arrangement to the, cathodes 4 of controllable gasor vapour-filled rectifying tubes 5:

The anodes B of these tubes are connected to the load 1 (for example the field winding of a directcurr'ent motor: tobe controlled) the other connection of which is connected in a usual manner to the earthed' neutral point A of the transformer 3. Parallel with theload'l, is connected;

by way of point'8 (and= A), a suitable control'-' apparatus which supplies a direct controlvoltage to terminals-l0 and II-, this voltage varying with the requirements imposed on the voltageof load-l. This-control -voltage which, in the present case, is 2V' (the direct voltage at the terminal H may be v+Vor V relatively to point I) is applied, by way of the secondary winding of the transformer, between the oathodes 4, and by way of a phase-shifting device, to the grids l2. The phase-shifting device is constituted by a resistance 13, a condenser 14, a resistance I and a condenser l6.

Consequently, the cathodes 4 carry an alternating voltage with respect to the neutral point A of the transformer 3. This is diagrammatically shown in Fig. 2 by the alternating voltage AK. Assuming that the ignition characteristic curve of the rectifiers coincide with the cathode potential, the line K thus also represents the ignition characteristic curve with respect to point A. In the present case, half the transformer voltage AK of transformer 3 is supplied to the grids l2 with a phase shift of approximately 90 produced by the phase-shifting device, as is shown in the separate vector-diagram, Fig. 3. In Fig. 2, the alternating voltage AK, having a consequent phase shift of 90, is shown as the alternating voltage GK, 1. e. the voltage set up between grid G (H!) and the cathode lead K (4). With respect to point A, the two voltages AK and GK may be added together,

since'they both occur across the grid circuit 12-4 5l 3E-i l-l llA-A-4. This summation yields a voltage AKG. In the case shown, ignition of that rectifier occurs, the anode voltage of which is positive relative to the cathode i. e. at point X, when viewed from the neutral point A. If the instant of ignition is considered relatively to the cathode line K (4), as is customary, ignition occurs at point X which, as far as the time is concerned, coincides with point X, as is indicated by a perpendicular broken line. By raising or lowering the summed voltage AKG with the use of the direct voltage +V or V, the rectifying tube concerned may be driven completely, i. e. theoretically with a phase-shift of from 0 to 180. If, in eifect, the control voltage is +V relatively to the zero line, as is shown in the figure, the summed voltage may be designated by AKG and ignition takes place at point Y at the beginning of the positive half wave. The rectifier then supplies its maximum voltage. If the control-voltage is reduced to V, the summed voltage drops to AKG and ignition takes place at the end of the half cycle which is positive for the anode of the rectifier i. e. at point Z. As stated, actual ignition relatively to the cathode 4 (K) takes place at the point of intersection of the phase-shifted alternating voltage GK and the zero line, the voltage GK also superposed on'the direct control-voltage +V or V likewise yielding ignitions at points Y and Z respectively.

In the circuit-arrangement shown in Fig. 1, the voltages are chosen to be such that the alternating supply voltage of each of the rectifiers, i. e. the voltage AK, serves itself as a compensation voltage for the grid and this in a reversed sense i. e. KA across the grid circuit, which is also due to the fact that the alternating grid voltage across G is taken, after the phase-shift, from KA. Thus, the compensation voltage KA (which serves as AK as a supply voltage), the direct voltage I0, II and the alternating grid voltage are operative throughout the grid circuit.

It is evident from the drawing that the peak voltage of GK, GK, should be approximately equal to the voltage V to ensure a maximum output. This peak voltage may, in reality, be slightly smaller than V, since the rectifier is not driven throughout 180 but, for example, 165 to 175 4 only. For the sake of simplicity, however, it is assumed that:

GK==V or GK= ,5

expressed in effective voltage.

In Fig. 3, the alternating voltages and phase shifts are shown as a vector diagram. The voltage vector GK (across condenser I6 in Fig. l) is at right angles to the vector CD (across resistance IS in Fig. 1). The resulting voltage DK is again at right angles to the vector DE (across resistance l3) Since the direct voltage I0, I I is not shown vectorially, point E may be assumed to be equal to point A, so that the vector KE=KA is equal to half the transformer voltage (Fig. 1) from which GK is derived.

From the vector diagram it follows:

GK= DK 2) and DK= KE /2 (3) GK= /2. KE /2=%;KE

KE=-2GK (4) On substituting (1) V GK=- V5 for (4) we have 2V KE==V 2 5 Since KE=KA (Fig. 3) this means that, if

half the transformer voltage is equal to /2 times half the direct control-voltage, the correct compensation is obtained. Thus, for example, if the mains voltage is 220 volts. then KA= volts; if the direct control-voltage of from +V to -v=2v=15e volts then v=7s volts and W5 is also 110 volts, so that condition '(5) is fulfilled.

To the ends of the secondary of the supply transformer 3, a second bi-phase rectifier circuit. is connected, the rectifiers I! of which are connected with their anodes l8 to the transformer. The control of these rectifiers takes place with the use of the saturated transformers L! which are connected between the grids 20 and the cathodes 2l. The cathodes are connected, by way of a second load to be controlled 22, to the earthed point A and thus have, relative to A, a variable direct voltage, which does not aifect the control of these tubes. The load 22 may, for example, be the armature of the direct-current motor, the field of which constitutes the load I. The load 22 may be controlled by shifting in phase the peaked voltages of the transformers 19 by means known per se (not shown for the sake of simplicity). The use of peaked voltages permits, as is known, a very accurate control of voltage. If the conditions imposed on the control are less stringent, use may be made of an alternating voltage superposed on a variable direct voltage for the control of the rectifiers H, which arrangement is more economical, since the saturated transformers 19 are less economical than a source of direct control-voltage 9. In this case, rectifiers I! may be connected by their cathodes to the transformer winding and be provided, similarly to rectifiers 5, with a control-device, the alternating cathode voltage being also compensated in a similar manner. Such a circuit is. shown in Fig. 4.

Instead of using the transformer 3, use may be made of an auto-transformer in the same circuit.

It frequently occurs that the available direct control-voltage does not-have the aforesaid value of 2V=156 volts which is obtainable only with the use of a very complicated control apparatus 9 (Fig.1).

In this. case satisfactory compensation is not possible.

The compensation voltage is obtained also with the use of an auxiliary transformer winding, which ,is preferably constituted by an auxiliary winding .of the supply transformer. Since the auxiliary winding need have a low power only, for example 0.1 w. with a rectifying power of 100 w., no difficulties are involved.

Fig. 5 shows a similar circuit-arrangement as Fig. 1, with the difference, however, that an auto-transformer comprising the compensation winding 23 is connected between the two resistances l3, whilst the direct voltage is connected to the centre 0. The vector diagram of this circuit is shown in Fig. 6 and is substantially the same as that of Fig. 3, from which it differs only by the added vector EC, equal to half the voltage of the total auxiliary winding 23. In a, manner similar to that described above, it follows:

KE:V (5) However, half the voltage of the auxiliary winding now is:

ECzKC-KE (6) EC:KC-V /2 ('7) and, since the alternating voltage KC is also equal to KA EC:KA-V /2 (8) If the line voltage is, for example, 380 volts and the direct control-voltage, for example, 100 volts, it follows: I

EC:19010o /:approximately 50 volts The auxiliary winding must then supply in total a voltage of 100 volts.

If the alternating mains voltage is again 380 volts and the direct control voltage 200 volts, we have:

EC:190-200 /2: 90 volt The auxiliary winding must then supply 180 volts and should be connected in the reverse sense, since EC is negative. The vector diagram then obtained is shown diagrammatically in Fig. '7.

If the mains voltage is 220 volts and the direct control voltage 156 volts, it follows:

in other words the auxiliary winding may be dispensed with, so that in principle the circuit-arrangement shown in Fig, 1 remains; however, it comprises an auto-transformer.

If, for some reason, a different phase-shifting circuit is desired use may, for example, be made of the circuit shown in Fig. 8, in which the phaseshift is obtained with the use of an inductance 24 with centre tap, a variable resistance 25 and a condenser 28. The voltage across the auxiliary transformer winding 23 should then be made higher as a function of the value of the inductance 24. In the case shown, the control device 9 is adjusted manually.

In a three-phase rectifying circuit, the arrangement may be as shown in Fig. 9. The line voltage terminals are designated 21, 28 and 29, to which the three-phase auto-transformer 30 is connected. The rectifying tubes 3| comprise grids 32 eachof whichis connected to an auxiliary winding 33 whose voltage is shifted in phase by 120? relatively to the cathode voltage, to 30 and theauxiliary transformer winding 34, the latter being connected in series with the auxiliary winding 33. The ends of the winding 34 are connected to the control apparatus 9 by means of which the direct voltage is adjusted. The latter is applied to the neutral point of the autoetransformer. The winding 34 contributes to thecompensation, the winding 33 yielding the 120 phase shift for the tube 3|. The further rectifiers are similarly connected. The control circuit of the tube shown on the extreme left has been omitted for the sake of simplicity. For the same reason, the rectifiers 35 of the second rectifying circuit are connected with their anodes to the transformer circuits 30and may, for example, be controlled in the manner shown in Fig. 1. V

The vector diagram of this circuit comprising tubes 3| is shown in Fig. 10.

Fig. 11 shows, in principle, a circuit-arrangement for the control-apparatus 9 proper, which may advantageously be combined with the circuits accordin to the invention. The voltage at the load "I is supplied to a control-apparatus 36 which acts upon the grid voltage of the auxiliary rectifying tube 31. The cathode of this tube is'connected, through a stabilizing tube 38,, to the centre A of the auto-transformer 3. The auxiliary tube 31 is fed from an auxiliary transformer 3B and is loaded by a resistance 39 with which a condenser 40 is connected in parallel for smoothing purposes. Owing to the interposition of the stabilizing tube 38, the cathode of the tube, 31 has, for example, a potential of +V relatively to point A. If the voltages across the control-apparatus 9 are such that the voltage across resistance 39 is adapted to vary, under the action of the control-apparatus 36, from 0 to V across the grid of the tube 37, the voltage at point I I will vary from +80V to '80V, which yields in the aforesaid direct control-voltage of +V to V.'

As stated, the circuit-arrangement of the control-apparatus 9 is particularly suitable for use in the arrangement according to the invention, since the auxiliary transformer 38 may be combined with the auxiliary transformer winding 23 shown in Fig. 5 which contributes to the compensation.

Such a combination is shown in Fig. 12, in which corresponding parts bear the same reference numerals. From the explanation of the operation of the circuit shown in Fig. 11, the operation of the circuit shown in Fig. 12 will be obvious. In this circuit the arrangement is further simplified and made more economical by the use of an auxiliary transformer 23 which supplies both part of the compensation voltage and the anode voltage for the control-apparatus.

What I claim is:

1. Rectifying apparatus comprising an alternating voltage multi-phase transformer provided with a winding having a neutral point, a plurality of multi-phase rectifying circuits coupled to said winding, each including a discharge tube having a cathode, a control electrode and an anode, the cathodes of the tubes in at least two of said circuits being connected to points on said windings at which relative to said neutral point an alter- 7. natingvoltage is impressed on the cathodes of the two tubes, direct-current load terminals connected between said neutral point on the winding and the anodes of said two tubes, a device coupled to said terminals for deriving a direct control voltage therefrom, and means separately connecting the control electrodes of the two tubes through said device to said neutral point to impress on said electrodes said control voltage in combination with an alternating voltage in a phase compensating for the alternating voltage on the related cathodes.

2. Apparatus, as set forth in claim 1, wherein said means separately connecting the control electrodes to the neutral point includes a phaseshifting network.

3. Apparatus, as set forth in claim 2, wherein said network provides a 90 shift in phase.

4. Apparatus, as set forth in claim 1, wherein said compensating alternating voltage is obtained from an auxiliary winding on said transformer.

5. Apparatus, as set forth in claim 4, wherein said auxiliary winding furnishes a voltage at least substantially equal to the alternating cathode voltage relative to the neutral point less the voltage V /2.

6. Rectifying apparatus comprising an alternating voltage multi-phase transformer provided with a winding having a neutral point, four multiphase rectifying circuits coupled to said winding each including a discharge tube having a cathode, a control electrode and an anode, the cathodes of the tubes bein connected to points on said windings at which relative to said neutral point an alternating voltage is impressed on said cathodes of the two tubes, a first pair of direct-current load terminals connected between said neutral point and the anodes of two of said tubes, a device coupled to said terminals for deriving a direct control voltage therefrom, means separately connecting the control electrodes of said two tubes through said device to said neutral point to imrpess on said electrodes said control voltage in combination with an alternating voltage having a phase compensating for the alternating voltage on the related cathodes, a second pair of direct-current load terminals connected between said neutral point and the anodes of the remaining tubes, a second device coupled to the terminals of the second pair for deriving a second direct control voltage therefrom, and means separately connecting the control electrodes of said receivin tubes through said second device to said neutral point.

'7. An arrangement, as set forth in claim 6, in combination with an electric motor whose field winding is connected to one pair of said load terminals and whose armature winding is connected to the second pair of load terminals.

8. Rectifying apparatus comprising an alternating voltage multi-phase transformer provided with a winding having a neutral point, two pairs of multi-phase rectifying circuits coupled to said winding each including a discharge tube having a cathode, a control electrode and an anode, the cathode of the tubes of one pair of said circuits being connected to points on said winding at which relative to said neutral point an alternating voltage is impressed on said cathodes of the two tubes, a first pair of direct-current load terminals connected between said neutral point and the anodes of said two tubes, a device coupled to said first pair of terminals for deriving a direct control voltage therefrom, means separately connecting the control electrodes of the one pair of tubes through said device to said neutral point to impress on said electrodes said control voltage in combination with an alternating voltage having a phase compen sating for the alternating voltage on the related cathodes, the anodes of the tubes of the other pair of said circuit being connected to points on said winding on either side of said neutral point, a second pair of direct-current load terminals connected between said neutral point and the cathodes of said other pair of tubes, and means to apply peaked voltages to the control electrodes of the other pair of tubes which are variable in phase.

9. Rectifying apparatus comprising an alternating voltage multi-phase transformer provided with a winding having a neutral point and an auxiliary winding, a plurality of multi-phase rectifying circuits coupled to said winding each including a discharge tube having a cathode, a control electrode and an anode, the cathode of the tubes of two of said circuits being connected to points on said windings at which relative to said neutral point an alternating voltage is impressed on said cathodes of the two tubes, direct current load terminals connected between said neutral point and the anodes of said two tubes, a device coupled to said terminals for deriving a direct control voltage therefrom, and means separately connecting the control electrodes of the two tubes through said device and a portion of said auxiliary winding to said neutral point to impress on said electrodes said control voltage in combination with an alternating voltage from said auxiliary winding having a phase compensating for the alternating voltage on the related cathodes, said device including an auxiliary rectifier coupled to another portion of said auxiliary winding to produce said control voltage.

ALFRED VAN DE WIEL.

No references cited. 

